Flashcards in AXIAL SKELETON: CRANIOVERREBRAL JOINTS Deck (21)
What is included in the craniovertebral joint?
1. Atlanto-occipital joint
2. Atlanto-axial joint (lateral and median)
*Atlanto-axial joint allows for rotation of the head
What is the Atlanto-occipital joint?
1. Between the lateral masses of C1 (atlas) and the occipital
2. Type of condyloid joint (Flexion: main movement; Extension; Limited lateral flexion and rotation)
*Cranium and C1 are connected by the AAO and PAO
*Help prevent excessive movement of the atlanto-occipital joints
What is the Lateral atlanto-axial joints?
1. Between the lateral masses of C1 and the superior articular facets of C2
2. Type of Plane Joint (gliding movement)
What is the Median atlanto-axial joint?
1. Between the dens of C2 and the anterior arch and transverse
ligament of the atlas
2. Type of Pivot Joint (trochoid or uniaxial)
3. Contains Transverse ligament of atlas (TLA): Very important
What is the Transverse Ligament of Atlas (TLA)?
1. Keeps the odontoid process against the anterior arch of the atlas
2. Extents between the tubercles of the medial aspects of the lateral masses of C1 vertebrae
*Odontoid process is more radiodense in an x-ray due to the overlapping of the C1 and C2 (den connects with C1)
What causes the rupture or injury of the Transverse ligament of the atlas (TLA)?
1. Trauma from vertical force (diving accident; fall from horse)
2. Connective tissue disease, which softens the transverse ligament of C1
3. Congenital anomalies from Down Syndrome causes lax or agenesis of the transverse ligament
What occurs during the rupture of the transverse ligament of atlas?
1. The dens is set free, resulting in atlanto-axial subluxation or incomplete dislocation
2. When complete dislocation occurs, the
dens may be driven into the upper cervical region of the spinal
cord, causing quadriplegia
3. Complete dislocation can cause the dens to be driven into the medulla of the brainstem, causing death
What ligaments strengthen the Median atlanto-axial joint?
1. Ligaments connecting the C2, especially the odontoid process, and the occipital bone
2. Cruciate ligament
3. Apical ligament of the dens
4. Alar ligaments
5. Tectorial membrane
What is the Cruciate ligament?
1. Strengthens the median atlanto-axial joint
2. Consist of the Transverse ligament of the atlas and two bands:
a. Superior longitudinal band (Passes to occipital bone)
b. Inferior longitudinal band (Passes to body of C2 vertebrae)
What is the Apical ligament of the Dens (AL)?
1. Arises from the tip(apex) of the odontoid process to the anterior margin of the foramen magnum
2. Strengthens the median atlanto-axial joint
What is the Alar ligament?
1. Short cords extending from the sides of the dens of the axis to the lateral margins of the foramen magnum
2. Prevents excessive rotation at the atlanto-axial joint
3. Strengthens the median atlanto-axial joint
What is the Tectorial membrane?
1. Upper section of the posterior longitudinal ligament
2. Passes posteriorly over the median atlanto-axial joint and its ligaments
3. Runs from the
body of C2 to the internal surface of the occipital bone (foramen magnum) and covers the alar ligaments and transverse ligaments of the atlas
*attaches to the clivus (internal surface of the basilar portion of the occipital bone)
What occurs in a fracture on the C2 vertebrae?
1. Common fracture (40-50%)
2. Affects the dens of the axis
3. Affects the vertebral body of the axis
What occurs in a fracture on the dens of C2?
1. Most common
2. May result from a lateral blow to the head
3. May result from a complication of a disease (osteoporosis or osteopenia)
4. Occurs mostly at the base of the den
*Delay or lack of healing due to the transverse ligament of C1 entering the fracture site causing instability of the joint
*Leads to avascular necrosis because of lack of blood supply to the separated fragments
What occurs in a fracture of the C2 vertebral body?
1. Occurs below the level of the base of the dens
2. Healing process is usually normal because the blood supply to the fragments is not affected and the transverse ligament of C1 does not interfere with the fragments
What occurs in the movement of the Atlanto-axial Joint?
1. Medial atlanto-axial joint and lateral atlanto-axial joint occur simultaneously
2. Permits rotation of the head
*During rotation of the head the cranium and atlas rotate as a unit around the pivot of the dens, which allows the head to move side to side (shaking of head: "no" movement)
What occurs in the movement of the vertebral column?
1. Intervertebral discs are the main sites of movement
2. Flexion: Greater in cervical region but less in the thoracic region
3. Extension: Greater in the lumbar region
4. Lateral flexion: Greater in the cervical and lumbar regions
5. Rotation: Greater in the cervical and thoracic region
6. Circumduction greater in the cervical and lumbar region
Where is the most common fracture in the vertebral column?
1. At C5/C6 (dislocation in forced flexion)
2. Sudden hyperflexion causes factures/ dislocation of the VC, which may cause a rupture on the ligamentum flavum
*Dislocation is uncommon in the thoracic and lumbar regions due to the ribs that interlock to the superior and inferior articular processes
What causes Hyperextension ("whiplash")?
1. Sudden hyperextension of the head and neck may injure the vertebral artery if the posterior arch of the C1 vertebrae is pinched between the occipital bone and C2 vertebra
2. May also cause a rupture of the anterior longitudinal ligament
3. Also, a fracture of the vertebral arch
*Common from a car crash or football injury
What occurs in a cervical spondylolysis of the C2?
1. From severe hyperextension of the head and neck
2. Fracture occurs in the Pars interarticularis (the bony column that connects the superior and inferior articular processes)
3. May cause rupture of the anterior longitudinal ligament and Anulus fibrosus of C2-C3 IV disc
*Ex: Hangman's fracture (hanging of a person causes severe hyperextension)